1. FIELD OF INVENTION
This invention relates to a novel process for the synthesis of 2,3-dimethoxy-5-methyl-6-substituted-1,4-benzoquinones having formula (I): ##STR2## wherein R is a group of the formula ##STR3## in which s is an integer of from 0 to 11, and A and D are hydrogen or A--B forms a direct bond.
Compounds of formula (I) are known as coenzymes Q, and especially, a compound of formula (I) in which A--B forms a direct bond and s is 9, namely 2,3-dimethoxy-5-methyl-6-decaprenyl-1,4-benzoquinone [2,3-dimethoxy-5-methyl-6-(3,7,11,15,19,23,27,31,35,39-decamethyl-tetracon tadecaen-2,6,10,14,18,22,26,30,34,38,-yl)-1,4-benzoquinone], is called coenzyme Q.sub.10 and is expected to show various clinical effects from the medicinal and pharmacological viewpoints because it participates in the electron transport system in living bodies and plays an important role in producing energies.